slow4dr
Member
- Joined
- Feb 19, 2017
- Posts
- 58
- Reaction score
- 96
I guess just a brief intro. My name is Jason and this is my Wife's '04 Denali. We're the 2nd owners and we've owned it for roughly 4 years. It mainly gets the kids back and forth to school and the BMX track. I currently work at a Hot Rod Suspension company with access to some pretty cool tools, software & engineers.
The truck has mostly been neglected, other than receiving routine maintenance. It's been a great truck other than the common dash issue. When we bought it, it had some ugly a$$ 24" wheels on it. Those were ditched in favor of some 17" MB wheels with Nitto 285/70 Tires. I cranked the stock torsions roughly 2", made some jounce spacers and had it aligned.
I've added a Spectre Intake, Magnaflow muffler, and '05 Electric fans. My buddies at Gio's Performance tuned it for me as well.
Recently, the truck started swaying in turns and scaring the wife. It was getting so bad that She refused to drive it on the freeway. So I crawled underneath and glanced at the stock rear bags. Both bags had holes in them and the shocks appeared to be leaking. After a little searching I realized that stock replacement bags were more expensive than a good aftermarket set of shocks(Bilstein or maybe Fox's).
This is where things took a turn for the..........expensive. After measuring the stock shock pickup points I realized that I could fit a longer shock in place. Then the light bulb went on when looking at some aftermarket lift kits. It appeared that the stock 4-link would allow for a lot more droop than the stock shocks/bags could offer. So I put the back of the truck on jack stands and removed the stock shocks/bags. Inch by inch I let the rear axle down taking measurements and noting where any issues arose.
The stock shocks allowed for roughly 3" of droop from ride height.(keep in mind the bags weren't functioning so would likely be less with them working)
Here is what I found once the stock shocks were removed at one inch increments.
4" droop(shock centers 23.750") = ABS sensor on the frame needs to be turned 90 degrees
5" droop(shock centers 24.750" = Panhard bar is getting to a pretty extreme angle(need to go back and get a pic)
6" droop(shock centers 25.750") = The brake line bracket on top of the axle needs to be bent up roughly 15-20 degrees. The anti-sway bar contacts the diff cover.
6.25" droop(shock centers 26") = 18" Strap limits travel(*NOTE* The panhard bar has pulled the axle over 1" from center)
Here are a few more measurements with the 18" strap removed.
7" droop(shock centers 26.75") = The stock springs become unseated. Ride height sensors come undone, the lower link bar hits the positive stop on the axle bracket
8" droop(shock centers 27.875) = ABS sensor needs to be relocated and diff vent needs to be longer, need longer brake lines(20" or more)
While I was in there I went ahead and removed the springs and went the other direction. There is roughly 4" of compression from ride height(again bags not functioning). The shock centers were 17" with full weight sitting on the bump stop.
After a little research I found a shock that would be perfect in a 6" droop/4" compression scenario(from current ride height).
2" FOA 10" Coilovers are 16.5" closed and 26.5" open - Technically these are about the same price as factory replacement bags. I added in 18" straps as they are also the perfect length in this scenario.
Now, you may be thinking "Wait, those are coilovers". I plan on eventually swapping these to the front and replacing the rears with something even longer but smooth body.
Doing a little mock up. Just a hair over 10.25" of total travel using 9" of the available 10" shock travel.
18" strap mounted to the anti-sway bar bracket and lower shock hole, fits perfect.
I bent the brake line bracket up a little using the handle of the jack.
ABS Sensor turned 90 degrees.
There is some empty area above the spare tire mount for the reservoirs.
A typical reservoir mount was too tall so I made some low profile ones. Basically just some 1"x.125" bar bent into submission. I cut a slit in it to allow the clamp and then welded the hole shut.
I will likely mount the reservoirs directly to the shock body once these are replaced by smooth body shocks.
This is why a typical roll cage type reservoir mount is too high. There is just barely enough room above the factory fuel tank fill line for the reservoir line. Anything taller than a tight up against the floor mount will hit the lines.
The driver's side reservoir fits in place with no issues. The reservoir fits right in between the body and the front of the shock mount.
The Passenger side needs some slight trimming of the body and inner panel to clear the reservoir line. Because of the rear A/C lines the reservoir has to be installed behind the shock mount and then the line needs to be lifted over to the front of the shock mount.
Unfortunately, the FOA provided misalignment spacers are for 1/2" bolts so I ditched them and made my own for the stock 14mm bolts. The shock needs to be offset .25" in the upper mount(to the outside) so the shock body doesn't hit the shock mount.
The anti-sway bar link modification was fairly easy. I just cut the stock links in half and threaded them 1/2"-20 L/H & R/H and then just made a corresponding L/H-R/H sleeve. I'm sure the CJ links would be sufficient too but I wanted to have some adjustment for future height changes.
This has made an incredible improvement in performance. I look forward to addressing the front suspension to even up the score. The back handles so damn good now that the front is terrible in comparison.
The truck has mostly been neglected, other than receiving routine maintenance. It's been a great truck other than the common dash issue. When we bought it, it had some ugly a$$ 24" wheels on it. Those were ditched in favor of some 17" MB wheels with Nitto 285/70 Tires. I cranked the stock torsions roughly 2", made some jounce spacers and had it aligned.
I've added a Spectre Intake, Magnaflow muffler, and '05 Electric fans. My buddies at Gio's Performance tuned it for me as well.
Recently, the truck started swaying in turns and scaring the wife. It was getting so bad that She refused to drive it on the freeway. So I crawled underneath and glanced at the stock rear bags. Both bags had holes in them and the shocks appeared to be leaking. After a little searching I realized that stock replacement bags were more expensive than a good aftermarket set of shocks(Bilstein or maybe Fox's).
This is where things took a turn for the..........expensive. After measuring the stock shock pickup points I realized that I could fit a longer shock in place. Then the light bulb went on when looking at some aftermarket lift kits. It appeared that the stock 4-link would allow for a lot more droop than the stock shocks/bags could offer. So I put the back of the truck on jack stands and removed the stock shocks/bags. Inch by inch I let the rear axle down taking measurements and noting where any issues arose.
The stock shocks allowed for roughly 3" of droop from ride height.(keep in mind the bags weren't functioning so would likely be less with them working)
Here is what I found once the stock shocks were removed at one inch increments.
4" droop(shock centers 23.750") = ABS sensor on the frame needs to be turned 90 degrees
5" droop(shock centers 24.750" = Panhard bar is getting to a pretty extreme angle(need to go back and get a pic)
6" droop(shock centers 25.750") = The brake line bracket on top of the axle needs to be bent up roughly 15-20 degrees. The anti-sway bar contacts the diff cover.
6.25" droop(shock centers 26") = 18" Strap limits travel(*NOTE* The panhard bar has pulled the axle over 1" from center)
Here are a few more measurements with the 18" strap removed.
7" droop(shock centers 26.75") = The stock springs become unseated. Ride height sensors come undone, the lower link bar hits the positive stop on the axle bracket
8" droop(shock centers 27.875) = ABS sensor needs to be relocated and diff vent needs to be longer, need longer brake lines(20" or more)
While I was in there I went ahead and removed the springs and went the other direction. There is roughly 4" of compression from ride height(again bags not functioning). The shock centers were 17" with full weight sitting on the bump stop.
After a little research I found a shock that would be perfect in a 6" droop/4" compression scenario(from current ride height).
2" FOA 10" Coilovers are 16.5" closed and 26.5" open - Technically these are about the same price as factory replacement bags. I added in 18" straps as they are also the perfect length in this scenario.
Now, you may be thinking "Wait, those are coilovers". I plan on eventually swapping these to the front and replacing the rears with something even longer but smooth body.
Doing a little mock up. Just a hair over 10.25" of total travel using 9" of the available 10" shock travel.
18" strap mounted to the anti-sway bar bracket and lower shock hole, fits perfect.
I bent the brake line bracket up a little using the handle of the jack.
ABS Sensor turned 90 degrees.
There is some empty area above the spare tire mount for the reservoirs.
A typical reservoir mount was too tall so I made some low profile ones. Basically just some 1"x.125" bar bent into submission. I cut a slit in it to allow the clamp and then welded the hole shut.
I will likely mount the reservoirs directly to the shock body once these are replaced by smooth body shocks.
This is why a typical roll cage type reservoir mount is too high. There is just barely enough room above the factory fuel tank fill line for the reservoir line. Anything taller than a tight up against the floor mount will hit the lines.
The driver's side reservoir fits in place with no issues. The reservoir fits right in between the body and the front of the shock mount.
The Passenger side needs some slight trimming of the body and inner panel to clear the reservoir line. Because of the rear A/C lines the reservoir has to be installed behind the shock mount and then the line needs to be lifted over to the front of the shock mount.
Unfortunately, the FOA provided misalignment spacers are for 1/2" bolts so I ditched them and made my own for the stock 14mm bolts. The shock needs to be offset .25" in the upper mount(to the outside) so the shock body doesn't hit the shock mount.
The anti-sway bar link modification was fairly easy. I just cut the stock links in half and threaded them 1/2"-20 L/H & R/H and then just made a corresponding L/H-R/H sleeve. I'm sure the CJ links would be sufficient too but I wanted to have some adjustment for future height changes.
This has made an incredible improvement in performance. I look forward to addressing the front suspension to even up the score. The back handles so damn good now that the front is terrible in comparison.
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